An Ancient Walk to Rewrite History
Since the 1970s, the predominant theory on the habitation of North America hinges on a land bridge from Asia. Approximately 13,000-16,000 years ago, near the end of the last Ice Age, climatic conditions precipitated a strip of land between Siberia and Alaska, called the Beringia land bridge. This theory is known as Clovis First because the people who traversed the bridge – the Clovis people – became the ancestors of modern Native Americans.
A slew of archaeological and genetic evidence supports this theory. Precious few tools have been unearthed that could predate the Clovis civilizations in North America. Further, DNA evidence suggests that as much as 80% of genetic material for all modern Native Americans comes from Clovis ancestors, with the rest deriving from populations that arrived afterward.
The theory is not a solid lock, however. In 2011, a site in Texas yielded artifacts from a group that predated Clovis by as many as 2,000 years. While this discovery certainly throws doubt onto the timeline of humans in North America, a 2018 discovery in White Sands National Park might blow the timeline all the way to the stone age.
Researchers have long known that ancient peoples inhabited the area that is now White Sands National Park. Paleo-Americans lived on the shores of the now-extinct Lake Otero, where they left evidence of hunting mammoths, camels, ground sloths, and bison. When the fertile nature of the region changed, megafauna and humans migrated away. These people lived and left the Tularosa Basin before dunes even existed there!
Not until approximately 4,000 years ago did humans resume activity in the basin, though it has seen relatively constant activity since then.
As impressive as it is to imagine an archaic human hunting mammoths in pre-White Sands, archaeologists uncovered a shocking fossil record that make those hunters look like new kids in the rocks.
The geology and climate of White Sands make it a veritable petri dish for fossilized footprints. According to the National Park Service, the park is home to the largest collection of preserved foot marks in the world.
Sometimes a researcher might stumble upon a new discovery; sometimes erosion slowly reveals fossils. Other times, an archaeologist needs to put in work.
At White Sands, the evidence of life is stratified.
The scientists found preserved footprints in layers below the surface, which opened up a potential bombshell. Geologists love layers. Stratification equates to dating. As periods come and go on our planet, one thing is constant: newer sediment goes on top of older sediment.
Dating by stratification is fantastic on lengthy time scales, but a bit harder on smaller ones. At White Sands, scientists got lucky. Underneath the footprints were preserved specimens of seeds from an aquatic plant called spiral ditchgrass or spiral tasselweed. They found other seed specimens above the prints. Organic material can be radiocarbon-dated. Testing the seeds produced a seismic result.
The footprints were between 21,000 and 23,000 years old!
If the radiocarbon dating is accurate, humans walked in New Mexico between 5,000 and 10,000 years before the land bridge would have allowed. This reality would be the definition of a paradigm shift when it comes to the peopling of North America.
Not all scientists are convinced about the results, however. The seeds come from an aquatic plant. Flora that live in water obtain carbon differently than above-ground plants. Water plants can pick up “old” carbon from other entities, in a process called the freshwater reservoir effect. This phenomenon might make a fossil seem older than it is when it’s carbon-dated.
White Sands researchers claim they took this effect into account and stand by the results. They studied hundreds of seeds from various layers and all the outcomes placed the seeds in proper geological eras. If the reservoir effect had tainted the study, the results would look a lot more random than they do, as the carbon that leeches into aquatic plants through that method is unpredictable.
Scientists are now attempting to collect enough pollen from the layers to carbon-date because it is not aquatic. Though they have high confidence in the info from the seeds, a second piece of evidence might silence all doubt.
The implications for the history of humans in North America are monumental in this study. For decades, we assumed glaciers had been barriers to living in these regions. How did they get there? And what happened to them? Even if humans did live on the continent long before the Clovis people, their DNA does not seem to be present in modern Native Americans. Were they wiped out somehow?
No matter the scientific outcome, an incredible human aspect to the footprints emerged at White Sands.
Amongst the singular prints left by humans and animals, researchers found a truly remarkable trail.
For nearly a mile, they uncovered the same footprints taking a walk. Anthropologists believe, based on size, gait, and walking speed, the marks belong to a young female. Astoundingly, they can discern that the woman carried something with her by the way her prints grew and slipped in the mud as she walked. Then they discovered what she was carrying: a toddler! Every so often, baby footprints appear next to the older ones. The woman carried the toddler as long as she could, sliding in wet soil, but occasionally she put the child down to walk.
That this jaunt was captured in the mud and preserved for thousands of years is simply astonishing. That we can determine what a person did that long ago through a fossil record is remarkable.
I recently took a hike with my toddler in these dunes. To feel the ancient connection between people is borderline spiritual. Some things about our species never change. Humans take their children for walks, whether next to dogs or mammoths.
What a blessing to live on this planet. I count myself fortunate to have walked where this woman and this toddler walked.
Further Reading and Exploration
Evidence of humans in North America during the Last Glacial Maximum – Science Magazine/American Association for the Advancement of Science
Prehistoric Footprints Push Back Timeline of Humans’ Arrival in North America – Smithsonian Magazine
The discovery of ancient human footprints in White Sands National Park and their link to abrupt climate change – USGS
Ancient footprints could be oldest traces of humans in the Americas – Nature